For younger children and their parents, Legoland at Windsor is a dream of a theme park. Big enough to be exciting, small enough for little legs to walk around, it feels safe, with wide, open paths that allow you to keep an eye on your children when they run ahead and too few white-knuckle rides to attract large groups of teenagers or people without children. There's enough indoor activity to make it bearable in bad weather, and even a few little details and jokes built into the bricks to amuse adults too.

We first took our son when he was two, and he was entranced by the trains moving round the models of European cities and landmarks built out of 28 million bricks in Miniland. We've been back a couple of times a year ever since, and now that he's almost five, he's more interested in the Brickadilly Circus fairground rides or in steering cars and boats around the courses in the Traffic Zone. His friend Alex, visiting for the first time, was amazed by pretty much everything.

Too young for the Dragon roller-coaster he'd seen in the TV ads, Alex rode instead on the Dragon's Apprentice. He was terrified, but afterwards declared it the best bit of the day. After seeing the realistic-looking moving dinosaur models nearby, he sighed that all his wishes except one had come true. Then he closed his eyes and asked, loudly, to find himself in Pokémon land. Sadly, we were unable to deliver that particular dream, but a hot chocolate and a doughnut from a food stall seemed to compensate nicely.

This was the first day of Legoland's Christmas season, and there were carols on the bandstand by the entrance. Lego Christmas trees were dotted throughout the park. The usual train had been decorated with snow and Christmas presents, with Lego models illustrating the 12 days of Christmas around the route. A 25-minute Peter Pan panto offers a welcome respite from the cold, although the people sitting in the middle did get covered in (soap sud) snow at the end.

But when it comes to Christmas, most kids want to see Santa. Last year, Legoland turned the circus tent into a toy factory, with rows of Lego reindeer in their stables and a rather distant Father Christmas appearing occasionally on a high balcony to wave at the children below. This wasn't too popular, so this year a closer encounter costs £2.50 per child extra.

By early afternoon, however, these had sold out, and the booth outside the tent was besieged by pleading parents who had promised their children they'd see Santa. If they'd known what was inside, they perhaps wouldn't have argued so strenuously. A recycled bit of last year's toy factory made the entrance seem exciting, but after that we shuffled slowly into a passage decorated with a few fairylights that was more grotty than grotto. The children were bored, stressed parents were arguing, a baby just up ahead cried interminably with nothing to distract her from her misery.

After waiting more than 45 minutes, the boys were ushered in by a wise-cracking assistant dressed as an elf, and sat awkwardly on stools at Santa's side for a photo (a further £3.99). He asked what they wanted for Christmas without once making eye contact or showing interest in their halting answers. Four-year-olds don't want ironic elves and world-weary Santas: they want to believe in the magic, and they should be indulged. Both of them left with a present of Duplo bricks, the biggest of which had flowers on. Alex said he'd give it to his little sister.

The park was advertised as open until 6pm, but by 4pm nearly all the little food and drink stalls dotted around it had closed. Most of the rides are ill-lit, and nearly all were operating with fewer staff, making the queues as long as they had been earlier. The paths around the park were murky, and a place that had seemed warm and welcoming despite the rain suddenly began to look sinister. Miniland was advertised as illuminated, but the lights turned out to be mostly in the trees. Many of the models were dark, and even when people could make out the shapes, they couldn't read signs explaining what they were. A few well-placed spotlights would have made all the difference.

But these are the carpings of an adult. The real critics should be our two nearly-five-year-olds. As we pulled out of the car park, I asked what they'd liked best. 'Everything!' they both cried. I pressed for details, but there was no reply. They were both fast asleep. And smiling.

Starter kit

Legoland is open 10am-6pm every day except Christmas Day until 7 January.

Tickets cost £18 for adults, £15 for children (aged three-15) and £12 for seniors.